This invention relates to suspensions for read-write heads used, for example, in disc drives, and more particularly to monocoque suspensions for read-write heads.
Conventional disc drives use a series of rigid discs with a magnetic coating to store electronic data. The data is stored in individually magnetized bits, and the bits are located in concentric circles, known as data tracks, on the surface of the rigid discs. The discs are mounted to a motor that provides high-speed rotation, while magnetic heads read data from, and write data to, the tracks. The hydrodynamic forces of a spinning disc cause the magnetic read-write head to hover over the surface of the disc at a relatively constant distance, and an actuator assembly moves the read-write head rapidly from track to track to read and write data.
The read-write head is suspended over a disc using a head suspension, which is connected to an arm of the actuator assembly. The head suspension is exposed to inertial stresses due to the rapid movement of the read-write head, but these inertial stresses may be reduced by decreasing the mass of the suspension. Also, the head suspension must have a high stiffness to avoid xe2x80x9covershootingxe2x80x9d the desired position of the read-write head over the disc, and to minimize amplitudes at resonant frequencies which are excited by the disc""s air flow. In addition to the stiffness, the resonance frequencies of the head suspension, such as the sway frequency and the first-torsion frequency, may be optimized to avoid excess vibration of the read-write head. In order to increase the stiffness of a head suspension while minimizing the mass of the suspension, a monocoque suspension design may be used. A monocoque head suspension may increase the moment of inertia of the suspension while removing mass from the center of the body. Then, the majority of stresses applied to the monocoque head suspension may be transmitted on the outer surfaces, while the stiffness of the suspension is increased.
An example of a prior art monocoque head suspension is disclosed in U.S. Pat. No. 5,731,931. This monocoque head suspension includes a load beam with a rigid floor region, and includes a shell region with a ceiling region that fits in an abutting complementary relationship over the load beam""s rigid floor region but where the ceiling region is separated and spaced from the floor region. The shell region has flanges along its perimeter that are attached to a top surface of the load beam using welds. The flanges and welds add mass to the suspension, which has the drawback of increasing the inertial stresses on the head suspension. Another monocoque head suspension is disclosed in related U.S. Pat. Nos. 5,734,526 and 5,894,655. This monocoque head suspension includes a load beam and a lamina, with recesses etched into either the load beam or the lamina. The load beam and lamina are affixed together with the recesses on the inside so as to form hollow chambers within the head suspension, and thus, a monocoque suspension. This monocoque head suspension has limitations that are best illustrated in comparison with the present invention, and thus, are discussed later.
The invention is directed toward a monocoque head suspension that overcomes the limitations of prior art suspensions. Generally, the inventive head suspension has a core positioned between a bottom skin and a top skin. The core has voids manufactured therein, such as cavities or channels, that create hollow regions between the bottom skin and the top skin.
In one aspect, the invention provides a monocoque head suspension for carrying a read-write head on a distal end and attachable at a proximal end to an actuator assembly. The suspension has a generally planar bottom skin having an interior surface and a top skin having an interior surface opposing the interior surface of the bottom skin. A core positioned between the bottom skin and top skin, and affixed to the interior surfaces of the bottom skin and top skin, has voids that form hollow regions between the bottom skin and top skin.
In different embodiments, the voids of the core are cavities that extend through the core. The cavities form hollow regions between the bottom skin and top skin. The core may be a polymer material, such as photoimageable epoxy. The bottom skin and top skin may both be made from a metal material, such as stainless steel, and therefore, the core material may be different from the material of the bottom skin and top skin.
In one embodiment, the core is a separately manufactured core positioned between the bottom skin and top skin and affixed to the interior surfaces of the bottom skin and top skin. The core may have voids therein that form hollow regions between the bottom skin and top skin. The core may, for example, have ridges formed therein to separate the bottom skin from the top skin. These ridges in one embodiment are positioned at least along most of a perimeter of the core, and there may be further ridges positioned generally in the center of the core. Alternatively, the core material may be corrugated. The corrugated core has a plurality of channels that form hollow regions within the monocoque head suspension. These hollow regions may extend generally parallel to the interior surfaces of the bottom skin and top skin, or utilizing advanced manufacturing processes may follow the outline of the suspension structure. The core may be made of a thin sheet of metal material, or alternatively, the core may be made of a polymer material such as polyamide, polyimide or silicon. The channels may have a cross-sectional pattern in the corrugated core, for example, the pattern may be a trapezoidal pattern or sinusoidal pattern.
In a second aspect, the invention provides a method of manufacturing a monocoque head suspension for a read-write assembly used in a disc drive. The method comprises providing a generally planar bottom skin having an interior surface, forming a polymer core on the interior surface of the bottom skin, and removing selected portions of the polymer core to form cavities through the polymer core. The method further comprises affixing a top skin on the polymer core so that the cavities in the polymer core form hollow regions between the bottom skin and top skin.
In another aspect, the invention provides a method of manufacturing a plurality of monocoque head suspensions for a read-write assemblies used in disc drives. The method includes forming a sheet of multiple identical bottom skins connected together in an array, a sheet of multiple identical cores connected in an array and arranged similarly to the array of connected bottom skins, wherein each of the cores are formed with ridges, and a sheet of multiple identical top skins connected in an array and arranged similarly to the array of connected cores and connected bottom skins. While the bottom skins, cores and top skins are connected in the arrays, the sheets of bottom skins, cores and top skins are aligned. Then, one side of each core in the sheet of cores is affixed to a corresponding bottom skin in the sheet of bottom skins, and an opposite side of each core in the sheet of cores is affixed to a corresponding top skin in the sheet of top skins.
In different embodiments of this method, a UV sensitive adhesive may be use to affix the core to the top skin and to the bottom skin. In this embodiment, small holes may be formed in the top skins and in the bottom skins for exposing UV rays therethrough to activate the UV adhesive material and spot adhere the core to the top skin and to the bottom skin. The method may further include thermally curing the assembly to completely affix the core to the top skin and to the bottom skin.
In another aspect, the invention provides an assembly to store data on a magnetic medium and read data from the medium. The assembly comprises a read-write head, an actuator assembly to position the read-write head over a specified location on the medium, and a monocoque head suspension carrying the read-write head on a distal end and attached at a proximal end to the actuator assembly. The monocoque head suspension is designed as discussed previously.
Advantages of the invention include one or more of the following. Monocoque head suspensions in accordance with the invention may have greater stiffness and reduced mass. The greater stiffness helps avoid the xe2x80x9covershootingxe2x80x9d problem. The greater stiffness also minimizes amplitudes at resonant frequencies, by increasing the resonant frequencies or by damping the amplitudes at the resonant frequencies. Also, manufacturing the head suspensions may be simplified because, for example, the core may be made of a photo-imageable epoxy, which only requires a lithography process to form cavities in the core and does not require an etching process and/or forming process. Further yet, the invention enables the designer to customize the resonance frequencies of the head suspension beyond the capabilities of the prior art head suspensions.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.